The present application provides for an improved method of enhancing carbon monoxide production while minimizing the associated hydrogen byproduct. Carbon dioxide is added to a monolith reactor producing syngas by catalytic partial oxidation of a hydrocarbon feed to reduce the hydrogen content and increase carbon monoxide content of the syngas.
Membranes are employed to separate the hydrogen and carbon dioxide from the carbon monoxide product and a reverse shift reactor is further employed to convert the hydrogen and carbon dioxide byproducts to additional carbon monoxide.
Certain industrial applications require a carbon monoxide purity of 98 to 99%, for example acetic acid manufacture. The hydrogen byproduct associated with carbon monoxide production has little economic value or at best fuel value.
The conversion of hydrocarbons to hydrogen and carbon monoxide containing gases is well known in the art. Examples of such processes include catalytic steam reforming, autothermal catalytic reforming, catalytic partial oxidation and non-catalytic partial oxidation. Each of these processes has advantages and disadvantages and produce various ratios of hydrogen and carbon monoxide, also known as synthesis gas.
Catalytic partial oxidation is an exothermic reaction wherein a hydrocarbon gas, such as methane, and an oxygen-containing gas, such as air, are contacted with a catalyst at elevated temperatures to produce a reaction product containing high concentrations of hydrogen and carbon monoxide. The catalysts used in these processes are typically noble metals, such as platinum or rhodium, and other transition metals, such as nickel on a suitable support.
Partial oxidation processes convert hydrocarbon containing gases, such as natural gas or naphtha to hydrogen (H2), carbon monoxide (CO) and other trace components such as carbon dioxide (CO2), water (H2O) and other hydrocarbons. The process is typically carried out by injecting preheated hydrocarbons and an oxygen-containing gas into a combustion chamber where oxidation of the hydrocarbons occurs with less than stoichiometric amounts of oxygen for complete combustion. This reaction is conducted at very high temperatures, such as in excess of 700° C. and often in excess of 1,000° C., and pressures up to 150 atmospheres. In some reactions, steam or CO2 can also be injected into the combustion chamber to modify the synthesis gas product and to adjust the ratio of H2 to CO.
More recently, partial oxidation processes have been disclosed in which the hydrocarbon gas is contacted with the oxygen-containing gas at high space velocities in the presence of a catalyst such as a metal deposited on a monolith support. The monolith supports are impregnated with a noble metal such as platinum, palladium or rhodium, or other transition metals such as nickel, cobalt, chromium and the like. Typically, these monolith supports are prepared from solid refractory or ceramic materials such as alumina, zirconia, magnesia and the like.